Longtan Dam: China's Tallest Roller-Compacted Concrete Dam

The **Longtan Dam** is the world's tallest roller-compacted concrete (RCC) dam, standing **216.5 meters** on the Hongshui River in Tian'e County, Guangxi Zhuang Autonomous Region, China. With an installed capacity of **6,426 MW**, it is a major power source for the energy-hungry provinces of Guangdong and Guangxi in southern China.

Introduction

Completed in 2009, Longtan Dam pioneered the use of RCC construction at unprecedented heights. Roller-compacted concrete uses a drier mix placed in thin layers and compacted with vibratory rollers, allowing faster and more economical construction compared to conventional concrete placement — a technique that proved especially advantageous given the dam's massive scale.

Engineering & Structure

• Type: Roller-compacted concrete gravity dam
• Height: 216.5 meters
• Crest Length: 832 meters
• RCC Volume: 4.61 million m³

Longtan Dam pushed the limits of RCC technology, which had previously been used only for dams up to about 130 meters. Engineers developed high-performance RCC mixes and advanced quality control methods to ensure the dam's structural integrity at 216.5 meters. The dam's crest extends 832 meters across the Hongshui River gorge, and its base is 190 meters thick.

The power station houses nine turbine-generator units, seven rated at 700 MW and two at 613 MW, arranged in an underground powerhouse. The dam's spillway can discharge up to 27,200 cubic meters per second, critical for managing the Hongshui River's monsoon-season floods, which can be severe in this subtropical region.

Geographic Setting

• River: Hongshui River (Pearl River tributary)
• Location: Tian'e County, Guangxi, China
• Coordinates: 25.03°N, 107.05°E
• Reservoir Capacity: 27.3 km³

The Hongshui River flows through some of the most spectacular karst terrain in southern China, where limestone towers, caves, and sinkholes dominate the landscape. At the dam site, the river passes through a deep gorge surrounded by forested mountains. The reservoir extends approximately 180 kilometers upstream through this dramatic karst landscape.

The region receives heavy monsoon rainfall — averaging 1,200 to 1,500 millimeters annually — making the Hongshui one of the most flood-prone rivers in southern China. Longtan Dam's reservoir provides critical flood storage, with a flood control capacity of 7 billion cubic meters that significantly reduces flood risk for downstream cities along the Pearl River.

Hydroelectric Power

• Installed Capacity: 6,426 MW
• Annual Output: ~18.7 TWh
• Transmission: Guangdong and Guangxi provinces

Longtan's 6,426 MW of installed capacity makes it one of the largest hydroelectric stations in China. The dam's annual output of approximately 18.7 terawatt-hours is transmitted primarily to Guangdong Province, home to the Pearl River Delta manufacturing hub, via high-voltage transmission lines. This clean energy displaces roughly 7.5 million tonnes of coal per year.

The dam's reservoir provides excellent regulation of water flow, enabling the power station to operate at high efficiency across seasons. During flood season, the turbines run near capacity as the reservoir stores excess water; during the dry season, controlled releases maintain steady power generation while supporting downstream water supply.

Environmental & Social Impact

• People Relocated: ~78,000
• Flood Protection: Reduces Pearl River basin flood risk
• Ecological Concern: Rare aquatic species in karst ecosystems

Approximately 78,000 people were relocated to make way for Longtan Reservoir, most from rural farming communities in Guangxi's mountainous interior. The resettlement process involved moving entire villages to newly constructed settlements, with compensation for lost farmland and housing. Integration into new communities and livelihood recovery remained ongoing challenges for years after relocation.

The reservoir flooded portions of a unique karst river ecosystem, affecting endemic fish species adapted to the fast-flowing, clear waters of the Hongshui gorge. The dam also blocks fish migration routes. However, the flood control benefits have been substantial, reducing catastrophic flooding that historically devastated downstream communities along the Pearl and Xi rivers.

Key Facts

• Longtan Dam is the world's tallest roller-compacted concrete dam at 216.5 meters.
• It generates 6,426 MW of hydroelectric power from nine turbines.
• The dam provides critical flood control for the Pearl River basin.
• Its reservoir holds 27.3 km³ of water in a dramatic karst landscape.
• Approximately 78,000 people were relocated during construction.

Fun Facts

• Roller-compacted concrete is placed so dry that heavy vibratory rollers drive over it like a road surface — Longtan's crews placed up to 3,000 cubic meters per hour using this method.
• The karst caves in the surrounding mountains contain some of the oldest and largest stalactite formations in southern China.
• The Hongshui River's name means "Red Water River," named for the reddish sediment it carries during monsoon floods.

Final Thoughts

Longtan Dam demonstrated that roller-compacted concrete technology could be scaled to heights previously thought feasible only for conventional arch or gravity dams. Its combination of enormous power output and flood protection makes it a cornerstone of water management in southern China's Pearl River basin.